Thrombus formation on indwelling venous cannulae in sheep : effects of time, size and materials.

Three experiments were performed to measure thrombus formation on plastic cannulae inserted by cut-down into veins of sheep. On polyethylene tubing, considerable thrombus was present after one day and the amount increased in the subsequent 13 days. When different sized polyethylene tubings were tested, thrombus tended to form in relation to the surface area. Smaller tubings had smaller proportions of their lengths covered with thrombus. There were differences between types of plastics with one batch of polyvinylchloride tubing being virtually non-thrombogenic.